===== ISTEM =====
Solve the following programming task.

TASK: Event Emitter

Write an 'EventEmitter' class with 'subscribe(eventName, callback)' and 'emit(eventName, args)' methods. The 'subscribe' method must return { unsubscribe: () => void }.

STARTER CODE (javascript):
class EventEmitter {
  // Write your code here
}

module.exports = { EventEmitter };


RULES:
- Keep the function name and signature EXACTLY as given.
- Return working code only. No explanations.
- Put the code in a single ``` block.
- Try to solve it first. If you genuinely cannot, write only this single
  line instead of producing faulty code: CANNOT_SOLVE

===== HAM YANIT =====
```javascript
class EventEmitter {
  constructor() {
    this.events = new Map();
  }

  subscribe(eventName, callback) {
    if (!this.events.has(eventName)) {
      this.events.set(eventName, new Set());
    }
    const listeners = this.events.get(eventName);
    listeners.add(callback);

    const unsubscribe = () => {
      listeners.delete(callback);
      if (listeners.size === 0) {
        this.events.delete(eventName);
      }
    };

    return { unsubscribe };
  }

  emit(eventName, args) {
    const listeners = this.events.get(eventName);
    if (!listeners) return;
    listeners.forEach(cb => cb(args));
  }
}

module.exports = { EventEmitter };
```